java ArrayList的实现

public class ArrayListDemo {
    public int size=0;//当前数组容量
    public int capacity=2;//默认容量
    public Object[] objects = new Object[capacity];

    public ArrayListDemo() {
    }

    public void add(Object object) {
        //检查数组是否已经装满，如果数组装满，数组容量扩大一倍
        if(capacity==size){
            capacity = this.capacity*2;
            objects = Arrays.copyOf(objects,capacity);
        }
        //添加数据
        objects[size++]=object;
    }

    public void delete(Object object) {//删除指定元素
        //遍历数组
        int temp = 0;
        for(int i = 0;i<size;i++){
            if(object==objects[i]){
                temp = i;
                break;
            }
        }
        for(int j=temp;j<size;j++){
            objects[temp]=objects[temp+1];
        }
        size--;
//        System.arraycopy(objects, temp+1, objects, temp, size-temp);
//        size--;
    }



    @Override
    public String toString() {//重写方法
        String str = "[";
        for (int i = 0;i<size;i++){
            str=str+" "+objects[i];
        }
        str=str+" "+"]";
        return str;
    }

    public void set(int i, Object object) {//修改数组
        if(i<0||i>capacity){
            System.out.println("超出数组大小");
        }
        for(int j=0;j<capacity;j++){
            if(i==j){
                objects[i-1]=object;
                break;
            }
        }
    }
}

public class ArrayListTest {
    public static void main(String[] args) {
        ArrayListDemo arrayListDemo = new ArrayListDemo();
        arrayListDemo.add(1);
        arrayListDemo.add("AA");
        arrayListDemo.add("##");
        arrayListDemo.add(6);
        arrayListDemo.add(5);

        System.out.println(arrayListDemo.size);//测试数组当前元素数量
        System.out.println(arrayListDemo);//测试查询

        //arrayListDemo.delete(6);//测试删除
        //System.out.println(arrayListDemo);

        //arrayListDemo.set(3,"hello");//测试修改
        //System.out.println(arrayListDemo);
    }
}